This invention pertains to a chain drive using a silent chain and in particular to a low noise chain drive composed of a silent chain and a plurality of toothed sprockets cooperating therewith. The silent chain has link plate sets successively connected for articulation by means of connecting members. Each set has a plurality of transversely aligned link plates with each having a pair of link plate teeth designed to engage the sprockets.
A conventional silent chain drive is shown in Japanese Laid-Open Patent Application No. 2-118231, in which link plate teeth have outside flanks each defined by an arcuate surface with the center consistent with the rotational axis of the link plate so that the outside flanks come in sliding contact with the sprockets to ease impacts and thereby lower noises from the chain drive.
Inevitably, however, when the outside flanks of the link plates and the sprocket tooth flanks of the sprockets are machined, there are flaws or imperfections usually in their profiles. These imperfections could hamper smooth sliding contact between the link plate teeth and the sprocket teeth and cause noise. Even if machined precisely, the link plate teeth and the sprocket teeth are subject to wear during the course of operation and eventually make noise.
A conventional silent chain drive of another type is shown in Japanese Laid-Open Patent Application No. 57-22443. In this design, a chain consists of two different kinds of link plate sets: link plates in some sets have inside flanks designed to engage the sprocket teeth and link plates in the other sets have outside flanks defined by a substantially straight surface coming into driving contact with the sprocket teeth. These two kinds of link plate sets are arranged randomly in the chain in order to randomize engaging timing with sprockets to reduce noises, especially pitch noises. Random arrangement of the different link sets is effective in reducing pitch noises but may not be as effective in easing impacts and, therefore, may not be as effective in reducing the overall noise level of the chain drive. Also, the link plates that contact the sprocket at their inside flanks are subjected to stress concentration at their crotches and may have a lower fatigue strength.
It is therefore an object of this invention to provide a low noise chain drive with link plate teeth and sprocket teeth of improved profiles that enable the link plate teeth to stay in sliding contact at their outside flanks with the sprocket teeth from the beginning of their engaging process through their completion and, after the completion of the engagement, remain stationary with respect to the sprocket teeth in order to ease engagement impacts.
Other objects of the invention will become apparent to one skilled in the art upon consideration of the following description and the accompanying drawings.